1. Field of the Invention
The present invention relates to a computer readable storage medium storing a 3-D (dimensional) game image processing program, a 3-D (dimensional) game image processing method, a 3-D (dimensional) game image processing program and a video game machine for drawing 3-D (dimensional) models comprised of a plurality of polygons in a virtual game space displayed on a monitor.
2. Description of the Related Art
In a game played in a 3-D space, a technique to express polygon models like animation by adding border lines has been known, where a polygon model is differentiated from an image to be the background by adding border lines (border exaggeration) so as to make the target polygon model stand out.
For example, Japanese Patent Laid-Open No. 2000-251094 states that when border lines are added to a 3-D model comprised of a plurality of polygons, data on the model to which border lines are added is read from a memory, an enlarged model where the model was enlarged at a predetermined ratio is created and stored in a memory once, geometry processing to overlay this enlarged model onto the original 3-D model is performed, the normal vector of the polygons of the enlarged model is inverted, then rendering processing to overlay both models onto the image to be the background is performed. By performing such image processing, a model where borderlines are added can be displayed on the monitor.
However, when border lines are added to a model by such an image processing method, the enlarged model must be temporarily held, which requires a memory to store the enlarged model. Also, as described above, geometry processing and rendering processing are required, and it takes time for these processings, so it is difficult to add border lines to many models as a game image display method which is required to display images at a predetermined frame cycle, and this method cannot be applied to 3-D video games. Also if a model for border lines is generated from an original 3-D model by a mechanical operation, as in the conventional method described above, the border lines sometimes deviate or border lines are not displayed due to the shape of the polygon model and the position of the view point of the virtual camera.
To solve the above problems, it is an object of the present invention to provide a 3-D game image processing program, a 3-D game image processing method, and a video game machine which do not require a memory to temporarily hold the enlarged model, decreasing the processing time required to add border lines to a 3-D model comprised of a plurality of polygons, and can be sufficiently applied to the display of game images which require adding border lines to many models
According to the present invention, a computer readable recording medium stores a 3-D game image processing program for drawing a model comprised of a plurality of polygons in a virtual game space. The 3-D game image processing program comprises the steps of: (a) storing a framed model; said frame model is made by: enlarging a 3-D model formed with a plurality of polygons; inverting a direction of a normal vector of each polygon constituting said enlarged model opposite to a direction of a normal vector of each polygon constituting said 3-D model to form a back model; and overlaying said back model on said 3-D model to form said framed model; and (b) drawing only polygons facing the direction of the viewpoint position of said virtual camera according to a drawing instruction of said framed model.
With the aforementioned features, a back model, where a direction of a normal vector of each polygon constituting an enlarged model which is acquired by enlarging a 3-D model is a direction opposite the direction of a normal vector of each polygon constituting the 3-D model, is overlaid onto the model and is stored in advance as a framed model. According to the drawing instructions of the framed model, the framed model is read from a recording medium, and based on the view point position of a virtual camera in the virtual game space and the direction of the normal vector of each polygon constituting the framed model, it is judged whether the polygon has a normal vector facing the direction of the view point position of the virtual camera. And only polygons which were judged as having a normal vector facing the direction of the view point position of the virtual camera are drawn.
These and other objects, features, and advantages of the present invention will become more apparent upon reading the following detailed description along with the accompanied drawings.
Note that throughout this specification the terms xe2x80x9c3-dimensionalxe2x80x9d and xe2x80x9c2-dimensionalxe2x80x9d are expressed as xe2x80x9c3-Dxe2x80x9d and xe2x80x9c2-Dxe2x80x9d, respectively, for short.